Evaluation of Slope Stability in Open Pit Mine and its Effects

摘要

Obajana Limestone Mine is operated by Obajana Cement Plc, the largest cement company in West Africa. The mine is located in Obajana town 49km North-West of Lokoja, Kogi State, Nigeria within the Igara-Kabba-Lokoja Schist belt with coordinates N07~0 55~1 00~(11) and E06~0 26~1 00~(11). An assessment of the mine pit slope face was carried out in order to evaluate bench slope stability conditions with a view to providing a consistently safe and effective mine pit working environment. Scanline method was used in the geologic mapping of a section of the northern pitwall of the mine. Empirical method was used to determine rock strength parameters relevant to design and analysis. Factors of safety values - the primary indices for assessing the probability or remoteness of slopes to failure were determined by the traditional limit equilibrium analysis; most accepted and widely used method among geotechnical engineers. Roclab and RockPack III Software were used as tools for the analyses. Results from kinematics analysis i.e. stereographic projections, stereoplots and stereo-analysis identified four sets of pole concentration with three of these lying within the friction cone (Critical area). This implies that the set of discontinuities with these poles will negatively influence stability conditions of the mine pit slope face.